This invention relates to novel compounds, specifically O- or S-(2-mercaptoalkyl)mono- or dihydrocarbyl carbamothioates and S-(2-mercaptoalkyl)mono- or dihydrocarbyl carbamodithioates and their use as collectors in the recovery of sulfide ores by froth flotation.
Flotation is a process of treating a mixture of finely divided mineral solids, e.g., a pulverulent ore, suspended in a liquid whereby a portion of such solids is separated from other finely divided mineral solids, e.g., clays and the like materials present in the ore, by introducing a gas into the liquid (or providing a gas in situ) to produce a frothy mass containing certain of the solids on the top of the liquid, and leaving suspended (unfrothed) other solid components of the ore. Flotation is based on the principle that introducing a gas into a liquid containing solid particles of different materials suspended therein causes adherence of some gas to certain suspended solids and not to others and makes the particles having the gas thus adhered thereto lighter than the liquid. Accordingly, these particles rise to the top of the liquid to form a froth.
An understanding of the phenomena which makes flotation a particularly valuable industrial operation is not essential to the practice of the present invention. Such phenomena appear, however, to be largely associated with selective affinity of the surface of particulated solids, suspended in a liquid containing entrapped gas, for the liquid on one hand and the gas on the other.
The flotation principle is applied in a number of mineral separation processes among which is the selective separation of such minerals as sulfide copper minerals, sulfide zinc minerals, sulfide molybdenum minerals and others from sulfide iron minerals.
Various flotation agents have been admixed with the suspension to improve the frothing process. Such added agents are classed according to the function to be performed: collectors, e.g., high carbon chain compounds such as collectors for sulfide minerals including xanthates, thionocarbamate, dithiophosphates, mercaptans, and the like; frothers which impart the property of forming a stable froth, e.g., natural oils such as pine oil and eucalyptus oil; modifiers such as activators to induce flotation in the presence of a collector, e.g., copper sulfate, depressants, e.g., sodium cyanide, which tend to prevent a collector from functioning as such on a certain mineral which it is desired to retain in the liquid, and thereby discourage a substance from being carried up and forming a part of the froth; pH regulators to produce optimum metallurgical results, e.g., lime, soda ash and the like.
These foregoing flotation additaments are selected for use according to the nature of the ore, the mineral sought to be recovered, and the other additaments which are to be used in combination therewith.
Xanthates and dithiophosphates are relatively inexpensive collectors but have a comparatively low activity as collectors, thus requiring larger concentrations than some other collectors to get satisfactory activity. The thionocarbamates have good activity as collectors but are relatively expensive to produce. Further, in the preparation of thionocarbamates, salt and odorous by-products are prepared. These by-products must be removed from the thionocarbamates.
There is needed a froth flotation collector which is relatively inexpensive to prepare which has a high activity as a collector for sulfide ores. There is further needed a collector which can be prepared by a process that does not produce salt or odorous by-products.